Meeting Abstract
How important is the role of time in evolution? Past research suggests that populations can rapidly evolve new dietary specializations and morphologies over extremely short amounts of evolutionary time. However, do morphological traits, particularly those related to functional innovation, evolve rapidly? We assembled the largest ever animal kinematic dataset from several of the most spectacular adaptive radiations on the planet, the cichlids of Africa’s Rift Valley. The three great cichlid lake radiations each contain the same set of ecological specialists, including fish specialized on algae, snails, plankton, scales, and other fish. However, they differ widely in age: Lake Victoria and its associated satellite lakes are roughly 100,000 years old, Lake Malawi is 1-2 million years old, and Lake Tanganyika is 10-20 million years old. We filmed feeding kinematics from all three major radiations, covering all major genera and ecological specializations. We then combined our kinematic data with a time-calibrated phylogeny encompassing the cichlid radiations to generate a phylogenetically corrected principal components analysis in R. We then used the SURFACE method to generate an adaptive landscape of kinematic traits. Only in the oldest of the three radiations, Lake Tanganyika, do cichlids colonize the full set of adaptive optima, with the younger radiations of Malawi and Tanganyika occupying fewer optima. Interestingly, Tanganyika’s extreme optima are characterized primarily by extreme jaw protrusion and extensive modification of cranial linkages, suggesting that while evolution can be rapid, true functional innovations require longer stretches of evolutionary time.
